In recent years, study of an ad hoc network in which wireless terminals are connected to each other in an autonomous and distributed manner progresses. In the ad hoc network, no access point is installed, and each wireless terminal relays a packet received from another wireless terminal (adjacent wireless terminal) connected to the wireless terminal to the adjacent wireless terminal on the basis of route information, and thus routes are formed.
In the ad hoc network, the network environment often changes as a radio field strength changes or a wireless terminal moves. Therefore, each wireless terminal connected to the ad hoc network performs route control before communicating with another wireless terminal.
For example, a case in which the route control is performed by a routing table method will be described. A wireless terminal newly connected to the ad hoc network broadcasts presence information indicating that the terminal is present on the network to the adjacent terminals. Then the adjacent terminals generate route information based on the presence information and broadcast the generated route information to the next adjacent terminals.
For example, each wireless terminal measures route quality between the terminal and the adjacent terminals, and when the terminal relays route information, the terminal relays the route information only to adjacent terminals connected to the terminal via a high-quality route (for example, Japanese Laid-open Patent Publication No. 2003-152786). For example, each wireless terminal broadcasts route information specifying a quality criterion to the adjacent terminals, and when the route quality does not satisfy the quality criterion, the adjacent terminals do not relay the route information (for example, Japanese Laid-open Patent Publication No. 2007-129542).
However, in the conventional techniques described above, the larger the number of wireless terminals connected to the ad hoc network is, the larger the amount of communication to control the route, so that there is a problem that the burden is placed on the network. As described above, each wireless terminal connected to the ad hoc network broadcasts route information to the adjacent terminals and receives response information. Therefore, as the number of the wireless terminals connected to the ad hoc network increases, the number of route information items and response information items increases exponentially, and thus the amount of communication to control the route increases.